1. Field of the Invention
The present invention relates to accessing data stored on tape.
2. Background Art
Tape is increasingly used as a data storage media due to its high volumetric data density and its low cost per bits stored. Typically, data is written onto tape with a tape head having a plurality of write elements for simultaneously writing data tracks. The tape head typically includes a plurality of read elements for simultaneously reading these data tracks. One tape head configuration includes two modules, each module having a plurality of write elements and associated read elements. The modules are arranged such that, for a given tape direction over the access head, the read elements precede the write elements on one module and the write elements precede the read elements on the other module. This configuration supports read-after-write in either tape direction.
When a tape access system is unable to read data written on the tape, the tape is typically rewound and an attempt is made to read the data again. This attempt is successful in most cases. However, this recovery effort takes a significant amount of time. The tape drive is required to stop the tape, run the tape backwards a small distance, stop the tape again, and then start the tape in the original direction of motion. This repositioning interrupts operation and causes performance degradation of the tape access system.
What is needed is to decrease the number of repositions during read back mode. Preferably, any decrease in repositions will be accomplished without significantly increasing the tape access system complexity.